This invention relates to the production of hard alloy deposits which are generally used in the manufacture of heat and wear resistant parts and cutting tools. More particularly, the invention relates to the production of deposits of alloys on substrates, or the production of free standing objects made from a deposit after removal of said substrate. The deposits of the invention have physical characteristics which are substantially improved over those presently known to those skilled in the art.
There have been many efforts in the past to improve the superficial hardness and strength of heat and wear resistant parts and cutting materials. It is known that the introducion of certain alloying elements into the surfaces of wear resistant cutting materials will improve the hardness of such materials. Exemplary of such elements are carbon, nitrogen and boron which may be used individually or in combination with other elements.
The introduction of such alloying agents into the surface of wear resistant materials has been accomplished by a number of different methods. One such method is by diffusion of the alloying agents into the surface of the material. This may be accomplished in a gaseous environment by a process referred to as "metallizing", or by a molten salt electrolysis referred to as "metalliding".
Another method which may be used separately from or subsequent to the aforesaid diffusion method is that of "over-coating" alloys onto the surface of such wear resistant materials. This involves the use of such materials as chromium carbide, titanium nitride, or titanium carbide which are deposited on the wear resistant materials to a thickness of about 1 to 10 microns, or as much as several hundred microns. These "over-coatings" may be applied by any one of the techniques known in the art as flame spraying, plasma arc spraying, reactive evaporation, sputtering, physical vapor deposition, or chemical vapor deposition.
The foregoing methods have generally improved the hardness of such wear resistant materials but have not made any significant improvement in the toughness or strength of such materials. In addition, alloys deposited by any of the foregoing materials have been found to have strengths that are generally less than the same alloys made by the techniques of forging, casting, or powder consolidation.
Accordingly, an objective of the invention is to improve the strength and toughness of such deposits whether they be used as coatings or as free standing bodies.
Another objective of the invention is to produce deposits of higher hardness than that achieved by conventional methods.
A further objective of the invention is to provide deposits with closely controlled compositions on extended areas of surface thereby to enhance their uniformity and chemical stability.